Area Forecast Discussion
Issued by NWS Brownsville, TX

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036
FXUS64 KBRO 120524 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1124 PM CST Mon Dec 11 2017

.DISCUSSION...Updated for latest aviation discussion below.
&&

.AVIATION...VFR conditions will continue with only upper level
cumulus and cirrus clouds moving overhead. Calm winds overnight
will increase out of the northwest late in the morning in the
wake of a dry cold front. Wind gusts of 20 to 25 knots will be
possible through sunset with no rainfall expected.
&&

.PREV DISCUSSION... /issued 602 PM CST Mon Dec 11 2017/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...Thick altocumulus with some upper level cirrus clouds
will continue to stream overhead this evening off a weak low near
Baja California. Light and variable winds overnight will increase
out of the northwest to 10 to 15 knots behind a weak cold front
Tuesday afternoon. Very dry air will keep precipitation chances
low with VFR conditions through the next 24 hours.

PREV DISCUSSION... /issued 254 PM CST Mon Dec 11 2017/

.Pleasant Weather Continues into Tuesday...

SHORT TERM (Tonight through Tuesday Night): A pretty strong and fast
moving 500 mb short wave will move south-southeast out of central
Canada pushing into the southeastern States later tonight into Tues.
This will usher a fairly weak and dry cold front through the region
resulting in a bit of a drop in temps and dewpoints Tues afternoon
and Tues Night. Significant CAA is pretty weak with this fropa and
freezing/near freezing temps do not appear to be much of a threat
throughout the short term.

The lack of deep layer moisture will continue to hold pops at 0%
throughout the short term period. The 12Z BRO sounding today showed
a very dry atms in place over the RGV due to no opportunity for
returning moisture since the winter weather last Fri.

Model temp guidance through tomorrow night is in decent agreement
for max/min temps. The NAM and GFS have a bit of a cooler bias
versus the ECMWF numbers. The high based cld cover that is moving
over the RGV from the closed 500 mb Baja Low to our west may be
enough to hold down the daytime highs a bit and to limit the
radiational cooling some at night. I`m going to opt towards the
warmer side of guidance for highs and close to a model blend for
lows.

Overall confidence in the short term forecast wording is above
average.

LONG TERM (Wednesday through Monday): The long term begins with
high pressure in control of the sensible weather across deep south
TX. Aloft, some slight ridging will be taking place between the
cut-off low across northwest Mexico and the highly amplified
longwave trough across the east. As the surface high continues
eastward, surface flow will transition to a southerly return flow
ahead of our next cold front due into the region Thursday
night/early Friday.

Speaking of the next front, globals suggest there wont be a harsh
cool down behind this frontal boundary. Although mostly dry,
there is some potential for isolated shower activity, especially
along the Rio Grande and coastal areas. This front pushes
through, however, begins to lift northward (as a warm front) as
early as Sunday. With the isentropic upglide ahead of the front,
did increase clouds a bit more on Saturday. Also, kept some slight
POPs in coastal/marine zones as there is a very slight signal for
shower activity. Temperatures wise, outside a slight reduction in
temps after frontal passages, MaxTs and MinTs should easily
rebound pretty quickly as winds quickly shift southeasterly and
begin to filter warmer/more moist air back into the region...still
looking at rather average temps, give or take a degree or two
respectively.

Frye/55

MARINE: (Tonight through Monday): A very light wind regime will
prevail throughout tonight and early Tues morning as weak surface
ridging remains in place over the region. The surface pressure
gradient will then strengthen some as the dry cold front moves
through the area tomorrow afternoon. This may increase the winds and
seas a bit as some stronger northerly winds spread over the region
tomorrow night. However the winds and seas will likely remain below
SCA levels through Tues night.

(Wednesday through Monday): Rather tranquil marine conditions can
be expected through the first portion of the long term. Winds and
seas will begin to increase late Thursday and especially on Friday
as a cold frontal boundary pushes through the region. Winds/seas
may increase to SCEC or low-end SCA thresholds early Friday.
Another cold front is projected to move through early next week
setting up an easterly fetch from Tampa to Brownsville, which will
have some implications on wave heights due to swells (depending
on exactly how long the fetch resides).
&&

.BRO WATCHES/WARNINGS/ADVISORIES...None.
&&

$$

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